Mass fish kill events caused by pollution, oxygen depletion, and disease cause enormous and largely invisible suffering.
Fish kill events are both ecological disasters and animal welfare emergencies. When agricultural runoff fuels algal blooms, the subsequent oxygen depletion can kill millions of fish in a single event. Fish dying from hypoxia show distress behaviors — surfacing, gill flaring, erratic movement — consistent with experiencing acute suffering. These events occur regularly across agricultural landscapes worldwide with minimal public awareness or regulatory consequence. Preventing fish kills requires addressing the root causes in agricultural runoff and water management.